A recent thread on the Theology forum that was closed before I could comment on it had touched on the difference between “belief” and “knowledge.” This is one of my particular areas of interest.
One can certainly have belief without knowledge. One can believe something that is simply not true. One has no knowledge it is true because it is in fact not true. One's belief is simply false.(
Or one can believe something that is in fact true, but for reasons that are false. The fact that what one believes is actually true is a matter of pure happenstance. One does not have knowledge, or even a belief that is justified. One has only an unjustified belief that happens to be true.
One can also have a belief that is entirely justified without actually knowing it is true. If one's mental faculties are operating properly and one has a sufficient basis in experience or evidence for what one believes, then one's belief is justified. It is not necessarily true, and one cannot say that one has knowledge it is true, but at least one is justified in believing it.
James 2:19 (NASB) states, “You believe that God is one. You do well; the demons also believe, and shudder.” Since the demons occupy the same (spiritual) level of reality as God, they may both believe and actually know that God is one. They know this in approximately the same direct way that I know my wife is a woman or my Ford is in my garage.
The interesting question is the sense in which we as Christians know God. I may believe in God, and my belief may be justified, but do I know Him? In what way (if any) do I know Him that the demons James is talking about do not?
As a Christian, I believe I am actually indwelt by the Holy Spirit. I know God, or at least believe I do, through the relationship I have with Him via reading His word, the indwelling of the Holy Spirit, and prayer.
In one sense, my “knowledge” of God may be less solid than that of the demons, who have direct knowledge of His existence and monistic nature that I don't. In another sense, my “knowledge” of God is far solider than that of the demons, since I have (or so I believe) an ongoing father-child relationship with Him while the demons have only their superficial knowledge of His existence and nature.
I think it is more accurate to say that Christians “believe” rather than “know.” Our experience of being indwelt by the Holy Spirit and communing with God through prayer strengthens the foundation of our belief and makes it supremely well-justified to us, but it is not really “knowledge” in the sense in which we ordinarily use the term or that makes sense to a non-believer.
This is why James talks of faith. Even when I have the solidest possible foundation of evidence and my belief is justified to the nth degree – for example, when I step onto an aluminum ladder that I have carefully examined – there is still an element of faith. I do not know the ladder will support me unless and until I make the tiny leap of faith of actually stepping onto it.
With Christianity, the leaps of faith are much larger – the leap that God actually exists and the additional one that, if He does exist, He is the God of Christianity. After we take these leaps and enter into a relationship with Him, we may use the language of “knowledge,” but in my view what we're really talking about is “a much stronger foundation for belief.”
I at least do not say that I know God exists or that, if He does, He is the God of Christianity. I say I believe these things. I demonstrate my faith, to God and to others, by trying to live my life as though what I believe is true, even though I cannot say I know it is.
Even as a Christian, I don’t find it convincing when fellow Christians speak of “knowing” things they really don’t know (especially when they suggest that those who don't use this confident language of "knowing" are somehow lesser Christians). I think it is fair, however, to suggest to a non-believer that he or she may, after committing to Christ, eventually arrive at a much higher level of certainty of belief (through the indwelling of the Holy Spirit, reading God’s word, and prayer) than seems possible in his or her current state of unbelief.
My closest analogy is with my direct experience of some paranormal phenomena. In my mind, I know they are real.
This is why some Near Death Experiencers have a disdain for non-experiencers. They know (they say) while non-experiencers merely believe (so if there is any area of disagreement, it's the non-experiencers who must be wrong).
I could say the same about the paranormal phenomena I have experienced. However, my experiences are not "knowledge" for anyone but me. They give me a very strong foundation for belief, and the beliefs I hold are justified by these experiences and a wealth of other evidence. But even in regard to these phenomena, I must acknowledge that I do not really know. I could have been fooled, my senses may not have been operating properly, or there may be an explanation entirely different from the one I attach to what I experienced. So, as with God, I never claim to know.